The present invention relates to a radio paging system and, more particularly, to a system for transmitting address signals and messages, as well as information common to a plurality of receivers, and a receiver applicable to such a system.
The art of radio paging systems with display has recently undergone remarkable progress so as to offer a character display service in addition to traditional numerical display services. The character display service allows a considerable quantity of information to be imparted to users of display oriented paging receivers.
The primary problem with such paging receivers is that the display function is wasted except for at the time of the reception of a call. Further, lack of optimal utilization can also be pointed out in regard to the paging station. The paging station does not emit a constant flow of radio waves and thus remains in an idle state except when calls are being originated. (If the pating station is constantly emitting radio waves, it transmit dummy signals except upon the generation of calls)
Additionally, in today's information-intensive society, there is an ever increasing demand for services which offer various kinds of information on a real-time basis and, in this connection, compact terminal equipment is desired.
Furthermore, if two or more address numbers were assigned to each paging receiver with one of these address numbers being common to all receivers so that information might be sent using the common address number, an information service which allows all the receivers to receive common information could be attained. However, the POCSAG code, which is internationally standardized by the CCIR as Radio Paging Code No. 1, hinders the creation of an efficient information service. More specifically, POCSAG code is such that to cut down power consumption at each receiver the indvidual address numbers assigned to the receivers are divided into groups, and are transmitted only at predetermined times, thus only those receivers for which an address number is intended turn on their power sources to receive a call. Common information cannot be imparted to all the receivers unless address numbers and common information each equal in number to the groups are transmitted, resulting in very poor channel utilization. Nevertheless should the address numbers not be grouped, the power consumption at each receiver would be increased.